Reduction of the amplitude of higher order harmonic frequencies in pulsed electrical signals

Reduction of RF emissions is very crucial for better EMI performance in electrical equipment,
for instance installed in automobiles. In this thesis, a flexible curve shaping module for a dcto-
dc PWM converter is developed to achieve efficient reduction of RF emission.
The design of the curve shaping module employs a programmable logic circuit (CPLD) where
a lookup table is stored with a certain reference curve shape. A D/A converter converts the
digital signal from the CPLD to analogue signal which is then fed to power stage to reproduce
the reference curve shape on the output. This output signal can be fed to electrical load. The
aim with the module is to employ different lookup tables corresponding to different curve
shapes resulting in flexibility of the circuit.
Frequency response for different curve shapes i.e. trapezoidal, sinusoidal and low pass filter
response were studied in theory for comparing their EMI performance. These curves are also
implemented in the real circuit for checking the response from the power stage.
By evaluating the practical circuit, it was found out that RF emissions were lowered
compared to hard switching techniques. Moreover various curve shapes were followed with
sufficient accuracy on the output of the power stage with resistive load. When inductive
loading is attached to the output of the power stage, the circuit enhances problems associated
with controllability.

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BibTeX @mastersthesis{Holst2004,author={Holst, Henrik and Himanshu, Jain},title={Reduction of the amplitude of higher order harmonic frequencies in pulsed electrical signals},abstract={Reduction of RF emissions is very crucial for better EMI performance in electrical equipment,
for instance installed in automobiles. In this thesis, a flexible curve shaping module for a dcto-
dc PWM converter is developed to achieve efficient reduction of RF emission.
The design of the curve shaping module employs a programmable logic circuit (CPLD) where
a lookup table is stored with a certain reference curve shape. A D/A converter converts the
digital signal from the CPLD to analogue signal which is then fed to power stage to reproduce
the reference curve shape on the output. This output signal can be fed to electrical load. The
aim with the module is to employ different lookup tables corresponding to different curve
shapes resulting in flexibility of the circuit.
Frequency response for different curve shapes i.e. trapezoidal, sinusoidal and low pass filter
response were studied in theory for comparing their EMI performance. These curves are also
implemented in the real circuit for checking the response from the power stage.
By evaluating the practical circuit, it was found out that RF emissions were lowered
compared to hard switching techniques. Moreover various curve shapes were followed with
sufficient accuracy on the output of the power stage with resistive load. When inductive
loading is attached to the output of the power stage, the circuit enhances problems associated
with controllability.},publisher={Institutionen för elteknik, Chalmers tekniska högskola},place={Göteborg},year={2004},keywords={CPLD, EMI, dc-dc PWM converter, power stage},note={144},}

RefWorks RT GenericSR ElectronicID 173940A1 Holst, HenrikA1 Himanshu, JainT1 Reduction of the amplitude of higher order harmonic frequencies in pulsed electrical signalsYR 2004AB Reduction of RF emissions is very crucial for better EMI performance in electrical equipment,
for instance installed in automobiles. In this thesis, a flexible curve shaping module for a dcto-
dc PWM converter is developed to achieve efficient reduction of RF emission.
The design of the curve shaping module employs a programmable logic circuit (CPLD) where
a lookup table is stored with a certain reference curve shape. A D/A converter converts the
digital signal from the CPLD to analogue signal which is then fed to power stage to reproduce
the reference curve shape on the output. This output signal can be fed to electrical load. The
aim with the module is to employ different lookup tables corresponding to different curve
shapes resulting in flexibility of the circuit.
Frequency response for different curve shapes i.e. trapezoidal, sinusoidal and low pass filter
response were studied in theory for comparing their EMI performance. These curves are also
implemented in the real circuit for checking the response from the power stage.
By evaluating the practical circuit, it was found out that RF emissions were lowered
compared to hard switching techniques. Moreover various curve shapes were followed with
sufficient accuracy on the output of the power stage with resistive load. When inductive
loading is attached to the output of the power stage, the circuit enhances problems associated
with controllability.PB Institutionen för elteknik, Chalmers tekniska högskola,PB Institutionen för elteknik, Chalmers tekniska högskola,LA engLK http://publications.lib.chalmers.se/records/fulltext/173940/173940.pdfOL 30